Mean TV detective found in decline? (7)
I believe the answer is:
average
'mean' is the definition.
('average' can be a synonym of 'mean')
'tv detective found in decline?' is the wordplay.
'tv detective' becomes 'vera' (I can't justify this - if you can you should believe this answer much more).
'found in' indicates putting letters inside.
'decline?' becomes 'age' (I've seen this in other clues).
'vera' put within 'age' is 'AVERAGE'.
Can you help me to learn more?
(Other definitions for average that I've seen before include "Medial" , "Mean - medium" , "Normal; mean" , "Arithmetic mean" , "'Medium, middling (7)'" .)